Add API Key Authentication to Search API

[dhirenmathur]

Description

The current search API in app/modules/search/search_router.py only uses bearer token authentication through AuthService.check_auth. We need to add API key authentication support to make it consistent with other API endpoints in app/api/router.py that use get_api_key_user dependency.

Current Implementation

Currently, the search endpoint is defined as:

@router.post("/search", response_model=SearchResponse)
async def search_codebase(
    search_request: SearchRequest,
    db: Session = Depends(get_db),
    user=Depends(AuthService.check_auth),
):
    # ...

Expected Implementation

The new endpoint should:

• Accept an API key through the X-API-Key header
• Reuse the get_api_key_user dependency from app/api/router.py
• Keep the same request/response models

Suggested Implementation Path

• Import get_api_key_user from app/api/router.py
• Update the search endpoint to use this dependency
• Add appropriate error handling for authentication failures